This was a single case study of a 54-year-old woman with a history of intermittent hypoglycemia of unclear etiology. Complaints included fatigue and dysarthria associated with home glucose levels of 60. On one occasion glucose was 18 mg/dl. A previous 72 hr fast on Gen Med Service revealed glucose in the 30's with concomitant decrease in insulin and c-peptide levels. An insulin-secreting, islet cell tumor was ruled out but the patient continued to have episodes of hypoglycemia. She was admitted to the GCRC for a 72 hour fast which was negative for organic hypogylcemia.